Circular Economy--Battery cascade utilization solution

June 19, 2020
(Reported by Kunming in this website): This week, the relevant departments of the company invited industry experts, environmental protection personnel and investment institutions to hold a seminar on the use of battery cascades after scrapping new energy vehicles in the beautiful spring city of Kunming Explore new modes!

       The panelists believed that in recent years, with the increasingly severe environmental problems, human living environment problems have become increasingly prominent, how to better environmental protection around the world has become a common research direction of all countries today. New energy has become the main force of environmental protection projects, and new energy vehicles have also emerged. As the core component of the battery, people's research directions tend to focus on how to improve performance, and ignore the battery disposal problem after the vehicle is scrapped. As a pioneer and advocate of the development and operation of new energy vehicles, Junfeng Company has the responsibility and obligation to explore the use of waste battery regeneration cycle ladders. First, it can find new business models, and second, it solves environmental problems in post-processing. 3. The third is to solve the worries of the automobile factory after selling vehicles.
Ke Shida lithium battery step utilization solution, let waste batteries play the waste heat

       Lithium ion batteries are widely used because of their advantages of light weight, small size, high energy density, long cycle life, long storage life, high consistency, high charge and discharge voltage platform, tolerable environmental temperature and no pollution. On electric cars.

       As far as my country's new energy vehicle industry is concerned, the power battery eliminated from the above has been tested. Although it is not suitable for on-board battery life, its energy storage capacity still has great practical value. By the end of 2020, the number of new energy vehicles in my country will reach 5 million. Since 2014, many vehicles have entered the scrap phase, how to turn waste into treasure.

      If it is directly disassembled, it is a great waste of the remaining use value of the battery. In addition to the internal chemical activity of these eliminated power batteries, the internal chemical composition of the battery is still intact, and the remaining energy of these batteries can still meet the family. The use of energy storage equipment in the field of daily energy storage, distributed power generation, and power exchange, backup emergency, etc. With the advancement of the technology and economic improvement of retired lithium batteries, the secondary utilization of lithium batteries will develop rapidly. So that the full value of the lithium battery can be fully utilized.
Lithium batteries retired from electric vehicles have large inconsistencies. The reasons for this inconsistency mainly include the following:

(1) The inconsistency of the battery's factory performance, the unevenness of the raw materials and the difference in the manufacturing process lead to the inconsistency of the battery, which is objectively produced.

(2) The different environment of the battery after leaving the factory, such as different ambient temperature, degree of self-discharge, air humidity, ventilation conditions, etc., will cause inconsistencies. (3) The inconsistency of the battery is further exacerbated during use. The maximum effective capacity of the battery pack is usually determined by the battery with the smallest effective capacity. Due to its long-term over-charge and over-discharge status, the aging rate will accelerate, forming a vicious cycle, resulting in a battery pack inconsistency. Expanding trends. (4) Different external use environments will deepen their inconsistency differences. There are some inevitable differences in the arrangement position, temperature and humidity, heat dissipation conditions, charging and discharging progress of each module in the battery pack, which increases the battery to some extent. Group inconsistency.

       The inconsistency of the battery is the biggest factor restricting its reuse, mainly including the state of charge (SOC), battery internal resistance, battery capacity, open circuit voltage and operating voltage, discharge platform time, rate performance, self-discharge rate, charge and discharge efficiency And influencing factors such as cycle life.
Ke Shida lithium battery step utilization solution, let waste batteries play the waste heat

      Generally speaking, the recycling process of obsolete batteries is usually failure treatment, disassembly of external structure, cell detection, screening classification, and then reused in steps. This process can reduce a certain degree of inconsistency, but the reduction is still very limited.

Traditional energy storage power stations use lithium batteries directly connected to the DC end of the energy storage converter (PCS) to control the charge and discharge of the battery through the PCS. In large-scale projects, due to the relatively large PCS power and battery capacity It will cause the huge data lithium batteries to be connected together in parallel to the PCS, and the charge and discharge control strategies are also completely consistent. In this way, the consistency requirements for lithium batteries are very high.

If you use a brand new lithium battery, because the factory has passed various tests, the products of the same manufacturer are more guaranteed in terms of consistency. Therefore, it will not cause a great impact in such projects, but because of the inconsistency caused by the production link, the manufacturer will also recommend an upper limit for the capacity of the parallel connectable lithium battery, in order to avoid all kinds of inconsistencies. problem.
        However, the inconsistency of retired batteries will be more serious, not only factors of different manufacturers and batches, but also the state of charge (SOC), battery internal resistance, battery capacity, open circuit voltage and working voltage, discharge platform time, Factors such as rate performance, self-discharge rate, charge-discharge efficiency, and cycle life.
      Take the problem caused by secondary use of battery SOC as an example. If the reusable lithium battery's normal reusable capacity is 30% to 80%, then during the charging and discharging process, there will be differences in SOC, and individual lithium batteries cannot be fully charged or discharged, so that they cannot fully retire The remaining value of the battery. If the traditional battery management system is still used at this time, it will be forced to be put into operation too early due to this "short board" when charging or discharging.

      At the same time, there are also factors such as battery internal resistance, battery capacity, open circuit voltage and working voltage, which can also cause adverse effects such as overcharge and overdischarge, battery circulation, heat and fire, and some may cause safety problems. And the inconsistent BMS system scheme because of different manufacturers is also an unfavorable factor for tiered utilization.

       In view of the various inconsistencies of the above-mentioned retired batteries, in order to better use the retired batteries in stages, some experts have proposed targeted products and solutions, that is, DC bus solutions implemented by DC-DC converters: lithium batteries Through multiple DC-DC converters merged into the DC bus, the DC end of the PCS is also merged into the DC bus, the AC end of the PCS is merged into the AC grid.

     Since multiple DC-DC converters are respectively connected to the lithium battery of the bus, the DC-DC converter can use different charge and discharge control strategies according to different retired batteries, and dock with different BMS systems, which can well avoid retirement. Battery inconsistency. Through the DC bus, the differential control of the retired battery is well decoupled from the rectification/inverter control of the PCS, so that the entire system runs optimally and stably.

      Experts and investors believe that in addition to solving the above-mentioned battery problems, there are many business models that can be discussed in depth and in detail. At present, the most important thing is to solve the problems of cognition, concept, policy, and law. Only in this way can the battery ladder use this topic and explore further and longer. (Xia Wu)